ポーセレンステインに関する基礎的研究

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In porcelain restoration, it may be often necessary to add some modifications in its contour, surface irregularities, or color matching before cementation. Stains are usually applied to match the shade of the porcelain with the surrounding teeth, or to give the characteristic details such as cracks, gingival stains and hair lines. Thus, the performance of staining depends significantly on the experience and skill of the dentist and technician. A number of studies have been reported about the porcelain surface texture produced by polishing or glazing, but the studies about the stain surface are very few. Therefore, the present study was undertaken to examine the changes in surface aspects and porosities of the fused stain by means of surface roughness test, colorimetric test and scanning electron microscopic observation. The porcelain blocks were prepared by polishing with a carborundum point, diamond point or sandpaper point, or glazing after polishing with the respective points. Then the stain was fused to each as-polished or glazed surface of the porcelain. The surface of the fused stain became smoother and glossier as the surface of the underlying porcelain was smoother. The surface roughness of the stain was minimized when the porcelain was polished with the carborundum point and glazed before the stain was applied. Although it is recommended by the manufacturer to fuse the stain at a temperature between 900 and 1, 100℃, the stain surface was markedly roughened with many hollows and incompletely melted stain particles when it was fused at 900 or 920℃. As the fusing temperature was elevated over 940℃, the stain particles appeared to be melted almost completely and the surface became satisfactorily smooth and glossy. However, the stain surface of the boundary area between the stain and the unstained porcelain was still roughened with many surface porosities. Abrasion by toothbrushing extremely changed the surface texture of the stain. Scratches by brushing were observed as expected, and besides, many craters appeared on the abrased surface. It is considered that those craters might be resulted from the exposure of the subsurface porosities due to the abrasion by brushing. Such craters may cause plaque accumulation and subsequent unfavorable tissue reactions. The cross sectional view of the stain by scanning electron microscope showed a number of porosities existing in the stain layer. No significant changes were recognized in size and number of the porosities by altering the finishing of the porcelain surface, the drying time of the slurry, or the fusing atmosphere. The occurrence of the porosities could be minimized when distilled water was used to mix the powder although it was a little more difficult to manipulate than in the case of using the annexed liquid or glycerin. Condensing the stain slurry was also effective markedly for diminishing the porosities. In considering the practical manipulation, therefore, it seems better to mix the powder with the annexed liquid diluted with distilled water and condense the slurry enough. It would be further advisable to apply the stain as thin as possible in order to decrease the porosities.
九州歯科学会の論文
1984-12-25

ポーセレンステインに関する基礎的研究

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